Stepper motor drive I/O port and serial com port?

Can anyone tell me why a stepper motor drive would have both an I/O port and a serial com port? I am supposed to get a stepper motor working for a school project and I have absolutely no electrical engineering knowledge. We have a Danaher 70360 stepping drive that is supposed to hook up to a DAQ box that is supposed to hook up to a PC card that is supposed to interface with LAB VIEW and do something. The Danaher manual umes the people reading it know what they are doing. So my question is what do the serial and I/O ports do? Are they supposed to do the same thing so that I use one or the other, or are they both supposed to be used?